Chemistry · Grades 9–12
Chromatography Rf
Measure both distances from the same origin. Rf is dimensionless and depends on the chromatographic conditions.
Rule and assumptions
Measure both distances from the same origin. Rf is dimensionless and depends on the chromatographic conditions.
Rf = spot distance / solvent-front distance
Worked examples
Measured from the same origin, a spot travels 95 mm and the solvent front 112 mm. Find Rf. Round to 3 decimal places if needed.
Rf = spot distance / solvent-front distance 95/112 = 0.848
0.848
Measured from the same origin, a spot travels 8 mm and the solvent front 65 mm. Find Rf. Round to 3 decimal places if needed.
Rf = spot distance / solvent-front distance 8/65 = 0.123
0.123
Try two questions
Measured from the same origin, a spot travels 14 mm and the solvent front 96 mm. Find Rf. Round to 3 decimal places if needed.
Measured from the same origin, a spot travels 42 mm and the solvent front 57 mm. Find Rf. Round to 3 decimal places if needed.
Answers and reasoning
Answers and marking notes
- 0.146
Rf = spot distance / solvent-front distance 14/96 = 0.146
- 0.737
Rf = spot distance / solvent-front distance 42/57 = 0.737
Further reading and review references
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Learning preview · independent educational and translation review required. Suggested grades are not official curriculum alignment.